Landslides – Prevention
Posted by Kshitija Nadgouda on June 8, 2006
In my earlier post, we discussed the causes of landslides. So logically the preventive measures can be deduced directly from the causes.
(Courtsey University of Kwazulu-Natal)
The first cause listed is gravity. Since we cannot alter gravity, what we can do, is alter geometry of the man-made slope so that the gravity effects are not detrimental. If the landslide is surficial (not too deep), the easiest way to prevent the fall of rocks and soil over the slope – is to vegetate it! However, vegetation can help only if the movement hasn’t already begun or if the landslide is deep!
Groundwater table changes are the most common cause of landslides. Heavy rains, leaking pipes, melting of snow in warm weather, floods, etc can cause changes in the groundwater table, thus inducing a landslide. Although natural phenomena such as heavy rains, melting snow, etc cannot be modified, its effect on the groundwater table can be controlled by applying the principles of hydrology and geotechnical engineering. Rain water or snow melt can be directed far away from the slopes by building drainage channels or swales that convey the water where it shall not be detrimental to the stability of the slope. Leaking pipes or leaking swimming pools can be easily fixed, once the location of the leak is determined.
(Courtsey BBC News)
Earthquakes cause ground shaking which may directly lead to a landslide. Or, the ground shaking may cause the soil to loosen and become weak, leading to a landslide. To prevent earthquake induced landslides, the ideal solution is to design the geometry of the slope such that it has an adequate factor of safety even for seismic cases.
(Courtsey Emergency Management Australia)
To prevent landslides triggered due to construction on top of the slope, a setback distance should be maintained between the top of slope and construction. The distance will depend on the type of construction and geology and geometry of the slope.
(Courtsey US Geological Survey)
Another cause of landslides (that I did not mention in my previous artice), is undercutting of the toe of slope. The toe of the slope plays a major role in keeping the upper portion in a stable condition. In fact, if a slope seems unstable, soil berms (counterweight fills) are placed at the toe of the slope to provide additional resistance to the potential movement of the upper part of the slope. Another aspect with similar principles would involve removing soil from the top of the slope, thus reducing the forces driving the movement.
Some good information on landslides is available at:
Copyright Kshitija Nadgouda.